I think it gives it a clearer indication that it's a version number, whereas "Society 5" either sounds like either yet another sequel to Society, or part of the

I think it gives it a clearer indication that it's a version number, whereas "Society 5" either sounds like either yet another sequel to Society, or part of the title itself. Also, point-oh sounds cool in English and just based on how much they use fractional percentages in Neon Genesis Evangelion, I assume it sounds cool in Japanese too.